The Felix M. Warburg House is a mansion located on 1109 Fifth Avenue and 92nd Street on the Upper East Side of Manhattan in New York City. The house was built from 1907 to 1908 for the German-American Jewish financier Felix M. Warburg and his family. After Warburg's death in 1937, his widow sold the mansion to a real estate developer. When plans to replace the mansion with luxury apartments fell through, the Warburgs donated it in 1944 to the Jewish Theological Seminary of America. In 1947, the Seminary opened the Jewish Museum of New York in the mansion. The house was named a New York City designated landmark in 1981 and was added to the National Register of Historic Places in 1982. The mansion was designed in the Châteauesque style by C. P. H. Gilbert and retains its original façade, characterized by French Gothic details around the windows and on the roofline. In 1993, Kevin Roche constructed an annex to the house in Gilbert's style built with stone from the same quarry that supplied the original mansion, replacing an extension built in 1963. The interior of the Warburg House, wholly occupied by the Jewish Museum, has a total floor space of . Critical reviews of the house's architecture have generally been positive with the exception of the 1963 extension. History In 1895, German Jewish banker Felix M. Warburg immigrated to the United States to marry Frieda Schiff, daughter of Jacob Schiff, head of the New York–based banking house Kuhn, Loeb & Co., which Warburg joined as a junior partner in 1897. After their honeymoon, the Warburgs moved into a townhouse at 18 East 72nd Street, a wedding gift to Frieda from her father. The Warburgs had five children by 1907 and, needing space, Frieda purchased a by lot at the northeast corner of Fifth Avenue and 92nd Street from Perry Belmont. At the time, the surrounding section of Fifth Avenue was known as "Millionaires' Row" because of its wealthy residents. Private residence To build a new residence on their lot, the Warburgs selected architect C. P. H. Gilbert, who was at that time building a house for Felix's brother, Paul, and had impressed the family with the mansion he built for Isaac D. Fletcher on Fifth Avenue. In August 1907, Gilbert filed plans for the house, which was to cost $260,000 (). By the next month, workers were excavating